The invention relates to a toggle which can be locked in a bore provided with a radial undercut surface in a manner which is positive and largely free of spreading pressure, having a toggle body of a diameter corresponding substantially to the diameter of the bore and introducible into the bore, locking elements being mounted thereto, whose ends facing the bore orifice can be deflected from a position within the diameter of the bore to a position in which they project at least partially beyond the diameter of the toggle body to engage the undercut surface of the bore.
A toggle of this kind is known (German Offenlegungsschrift No. 25 35 066), in which the toggle body consists of a heavy sleeve insertable into the bore, and provided in the area of its bore-internal end with recesses in which fluke-like locking elements are disposed which are biased by a spring to the expanded position in which their ends facing rearwardly toward the bore orifice are capable of engaging the undercut surface of the bore. Prior to the introduction of this toggle into the corresponding bore, the locking elements are held by a ring in the retracted position, the ring being disposed on the outside of the locking elements such that, when the toggle is inserted into the bore, the ring is forced downwardly by the locking elements. Alternatively, embodiments of the toggle are known in which locking elements carried radially displaceably in recesses in the sleeve are displaceable by a cam or spreader from the position in which they are withdrawn within the bore diameter to the expanded locking positions. For the locking action, it is then necessary to introduce a special tool into the toggle whereby the cam or spreader is rotated. For the fastening of workpieces, these known toggles have in their end facing the bore orifice an internal thread into which screws can be driven to hold the workpiece. In any case, however, the procedure in the known toggles is first to place the toggle in the prepared and undercut bore, then place the workpiece in the desired position over the bore, and then pass the bolt through the hole in the workpiece into the toggles and tighten it. This procedure is not only complex, but it also has the disadvantage that one must check carefully before fastening the workpiece to see whether all of the bores are actually provided with a toggle. Because if due to an oversight no toggle has been placed in one or more bores, the workpiece, which possibly may already have been fastened with several bolts, must again be taken off and, after the missing toggles have been installed, it must be fastened on again.
In contrast, the object of the invention is to create a toggle which can be locked positively and without expansive pressure against an undercut surface of a bore, and which does not have to be installed before mounting the workpiece but can be inserted through the hole in the workpiece into the bore. Furthermore, the locking elements are to be positively expanded to the locking position without requiring a special tool for the purpose.
Setting out from a toggle of the initially mentioned kind, this problem is solved in accordance with the invention by providing the toggle with a bottom piece of relatively short length disposed on the bore-internal end of an elongated bolt, and supporting the bore-internal ends of the locking elements which close together to form a thick-walled cylindrical sleeve surrounding the bolt, providing the bolt with a component tapering conically towards the interior bottom of the bore and entering between the ends of the locking elements facing the bore orifice so that, when the bottom piece is displaced towards the bore orifice the rearward ends of the locking elements will be positively deflected radially outwardly, and providing the bolt on its outer end with a bolt head or a nut screwed onto a thread of the bolt. The toggle thus constructed is insertable through a hole in a workpiece, and the bolt head or nut plus washer, if any, projecting from the hole in the workpiece will show at a glance where a toggle has been set and where one has yet to be placed.
The conically tapering component is preferably formed of the conically tapering bore-internal end of an elongated sleeve placed longitudinally displaceably on the bolt, its length being approximately equal to the distance between the bore undercut and the outer surface of the workpiece being fastened, plus the tightening distance required for the expansion of the locking elements. Since the length of the sleeve depends on the depth of the undercut surface in the bore and the thickness of the workpiece to be installed, it is recommendable to use for the creation of the undercut a tool which has a depth stop which is adjustable or adjusted to the required depth of the undercut, holding the workpiece in place so as to allow for its thickness during the boring of the undercut, or, if the workpiece is too heavy or bulky, using a gauging collar corresponding to the thickness of the workpiece.
In an alternative embodiment of the invention, the conically tapering component is formed of a conical section of the bolt itself, whose shank adjoining the conical section on the bore orifice side has a diameter equal to or only slightly smaller than the diameter of the bore. In this manner, a large cross-sectional area is made available in the critical, shear-stressed portion of the bolt.
To prevent the toggle from turning as a whole when it is being set in the bore, so that the locking elements are unable to expand and engage the undercut surface, the bottom piece has, in further development of the invention, antirotational means engaging the wall of the bore. These means can be, for example, resiliently deformable claws projecting radially star-wise from a ring disposed on an indent in the bottom piece, it being possible to produce the ring integrally with the holding claws from plastic, since then it is possible to make it inexpensively by the injection molding process.
Alternatively, antirotational means can be provided which are stamped out of spring metal and are similar to the star lock washers used for locking machine screws, or they can be made of spring wire with projecting extremities.
It is recommendable to provide a screw thread on the bolt, at least on its bore-internal end, and to drive it into a complementary thread in the bottom piece. The effective bolt length can thereby be varied to a certain extent and, if a headed bolt is used, the threaded connection serves for the drawing up of the bottom piece when the locking elements are to be expanded.
If a nut is provided which is threaded onto a thread on the outside end of the bolt, it is recommendable that the length of the thread on the bolt be at least equal to and preferably longer than the tightening length required for the spreading of the locking elements.
However, in the case of an embodiment in which a sleeve is placed on the bolt, the bolt can also be a headless bolt threaded on its full length. In either case, it is recommendable to provide a screwdriver slot in the outer end surface of the bolt for engagement by a screwdriver or other such tool.
In a further development of the toggle of the invention, a circumferential radial groove is provided in the outer sides of the locking elements confronting the bore wall, and a resiliently expandable ring is disposed therein to hold the locking elements in the retracted position; the ring can be either a full ring of rubber elastic material, or preferably a jump ring of spring steel wire.
The locking elements can be supported on the bottom piece by providing the bottom end of each locking element supported by the bottom piece with at least one projection which engages a matching recess in the bottom piece and thus prevents the locking element from turning circumferentially relative to the bottom piece, without interfering with the expansion of the upper ends of the locking elements. Alternatively, two projections can be provided on each locking element, preferably adjacent the lateral edges thereof, engaging recesses in the bottom piece.
In an embodiment of the toggle of the invention in which a sleeve is provided, the sleeve, as previously stated, must be adapted relatively precisely to the given depth of the undercut surface and to the thickness of the workpiece. Less critical in this regard is an embodiment in which the sleeve is axially deformable to a certain extent under the action of axial forces. A sleeve that is too long is then compressed axially by the required additional amount simply by tightening the bolt head or nut, as the case may be.
In the simplest case, the sleeve has for this purpose at least one circumferential groove reducing its wall thickness, the remaining thickness of the sleeve wall being so small that it is compressible in the necessary manner.
Alternatively, an annular element which is compressible in the axial direction can be provided between the sleeve and the screw head or nut provided on the bolt.
The securing of the toggle against rotation in the bore when it is being set, i.e., when the locking elements are being expanded, is brought about in another embodiment of the invention by the fact that the component which tapers conically towards the interior of the bore and is inserted inside of the locking elements is a spreader cone of relatively great angle of conicity which is disposed on the bolt, and this spreader cone is joined to an additional spreader cone whose tapered end points toward the bore orifice, and whose angle of conicity is smaller than that of the first spreader cone; the latter tapered end is inserted into the bore-internal end of a sleeve which is also disposed for longitudinal displacement on the bolt and is divided by slots into spreadable segments along at least part of its length. The deformation resistance of the ring, together with the resistance, if any, which the mounting of the locking elements on the bottom piece offers to the expansion of the locking elements, is made such that it offers to the expansion of the locking elements a resistance which is greater than the resistance offered by the segments of the slotted sleeve to expansion. The expandable ring holding the sleeve segments together and selected in the manner described above as to its resistance to deformation by expansion, in conjunction with any additional resistances to the expansion of the locking elements, assures that the spreading of the sleeve and that of the locking elements will take place in the required sequence.
In an advantageous further development of the invention, the spreader cone of greater angle of conicity is joined to the spreader cone of the smaller angle of conicity by a spacer element which is deformable in the axial direction and whose resistance to deformation by axial compression is greater than the resistance which is offered by the ring holding the locking elements together, plus the resistance, if any, offered by the means whereby the locking elements are held on the bottom piece, to the expansion of the locking elements. This spacing element has the purpose of permitting an additional axial tightening of the already outspread locking elements in case the locking elements have not yet been drawn all the way to the undercut surface after complete expansion in the installation procedure, so that such a toggle would have a slight looseness in the axial direction. By additional turning of the nut on the bolt or of the head of the bolt, as the case may be, such a toggle can then be tightened and installed under axial tension by the deforming of the spacing element until the locking elements are completely engaged.
The bottom piece bearing the locking elements is preferably in the form of a short, cylindrical body in whose upper surface facing the bore orifice pockets are formed which are engaged by projections extending into them from the bottom ends of the locking elements. The locking elements are secured against rotation by these projections.
To prevent the bottom ends of these projections from being forced against the bolt when the locking elements are expanded to the locking position, thereby damaging the thread whereby the bolt is held in the bottom piece, provision is made in a further development of the invention for the pockets to be closed off from the bore receiving the bolt, at least in their bottom portion and for the projections to be correspondingly reduced in thickness at their extremities.
Alternatively, the projection can also be made thinner overall, so that it will have the thickness of the terminal portion over its entire length, for example. A separately made ring is then inserted into the interstice between the bolt and the projection.
At the same time, it is recommendable for the pockets in the bottom piece and the holding projection of the locking elements to be provided with matching cross-sectional shapes differing from the circular cross section, in order to assure that the locking elements will be fixed in correct alignment with the bottom piece.
The projections are preferably integral with the locking elements and have in the area where they join the locking element a reduced cross section permitting the locking element to be bent in the desired direction relative to the projection. Such a construction of the expandable mounting of the locking elements on the bottom piece is very easy and inexpensive to realize, since it avoids the need for complex hinging involving links and journals.
The bottom faces of the locking elements are preferably flat surfaces at right angles to the longitudinal central axis of the toggle, while the end face of the bottom piece supporting the locking elements is beveled in the areas confronting their end faces in such a manner as to accommodate the anticipated bending of the locking elements. When the toggle is in the installed state, the bottom faces of the locking elements are therefore provided with a broad area of support on the beveled portions of the bottom piece, thereby assuring that they will have a broad base capable of withstanding heavy stresses.
The spreader cone of large angle of conicity and the spreader cone of small angle of conicity as well as the spacing element are preferably combined into a single, double conical spreading element so as to simplify the assembly of the toggle, although it would, of course, be also fundamentally possible to make these parts separately and assemble them individually. Then, however, care would have to be taken so that they would be unable to be turned relative to one another in the assembled toggle.
For the sake of simple and inexpensive manufacture, the spreader cones and the spacing element can be injection molded in one piece of plastic.
The spacing element is then desirably formed of at least two, preferably three or more legs disposed at equal angular intervals, joining together the two spreaders.
Alternatively, the spacing element can also be in the form of an axially collapsible sleeve at whose opposite ends the two separately made spreade cones are disposed in a non-rotatable manner. In this case the sleeve can be, for example, a thin sleeve of sheet metal, while the spreaders can again consist of plastic or alternatively also of metal.
Spreader cones made of metal can also be combined with a sleeve made of plastic, this sleeve then constituting the deformable spacing element.
In order to assure that the parts of the toggle which are arranged successively axially on the bolt will be unable to turn relative to one another when the toggle is tightened up, thereby impairing the setting operation, at least one rib-like projection is provided which extends from the conical spreader surface and engages the gap between two locking elements or the gap between two spreading segments of the sleeve.
In this case it is recommendable for the ribs of the spreader facing the locking elements to extend so far beyond the bottom end of the spreader towards the bottom piece that their bottom ends will just engage the bottom piece when the locking elements are in the properly expanded locking position. The projecting ends of these ribs serve as stops to prevent the spreader cone from being driven too far within the locking elements, and to prevent the locking elements from being spread open beyond the locking position.
Lastly, it is recommendable to provide the spreader cone engaging the spreading segments of the sleeve with a radially projecting circumferential bead which is engaged by the free ends of the spreading segments of the sleeve after they have been spread to a given extent. The bead also acts as a stop to prevent excessive expansion of the segments of the sleeve.